The change of the over-current protection point of the power switches, caused by slope compensation, is analyzed in detail. It is discovered that the peak current protecting value increases as the duty cycle decreases. As a result, the safety operation of the switches is damaged greatly. A novel solution to improve over-current protection with constant peak current limitation is proposed by inducing synchronous slope compensation into the current limit function instead of the original constant voltage. The design principle and method of the protection circuit based on a UC3846 PWM controller for the interleaved dual-forward converter is presented. Experimental results are given to verify the analysis.
G.-M Chen, J.-L Cao and X.-C. Wang, “Design and Implementation of Ramp-Wave Generator in Peak Current Controlled BOOST DC-DC Converter,” Journal of Shanghai University, Natural Science Edition, Vol. 8, 2004, pp. 357-361.